Friction stir weld plugs and methods of using thereof

ABSTRACT

In one aspect of the disclosure, an article for filling an opening in an object includes a plug having a body, a first flange, and a second flange. The plug has a trailing end. The first flange is in contact with the body and extends away from the body. The second flange is in contact with the first flange and extends away from the first flange and the body. The second flange is configured to deform toward the body upon installation of the plug into the opening. This deformation of the second flange rotationally and translationally secures the plug in the opening and consolidates the plug in the opening.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.14/043,596, entitled “FRICTION STIR WELD PLUGS AND METHODS OF USINGTHEREOF,” filed on 1 Oct. 2013, which is incorporated herein byreference in its entirety for all purposes.

BACKGROUND

When parts are joined using friction stir welding, intersecting weldsmay often be performed. For each weld, an opening is formed at thelocation where the welding tool exits the parent material. Weld-exitopenings are generally not desirable, particularly when a subsequentweld traverses the opening. Specifically, welding over an opening maycause voids in the weld nugget, thereby reducing the joint strength andcreating surface imperfections due to the volumetric material deficiencyin the weld. Various approaches for filling weld-exit openings have beenproposed. For example, wedges having polygonal cross-sections may bestaked into the openings using punches and hammers. However, thisprocess is time consuming and only marginally effective since thepolygonal cross-sectional shape of the wedges produces voids uponinstallation of the wedges into the parent material. Furthermore, thestaked wedges may be ejected from the openings during the subsequentweld. Alternatively, reaming out the openings and press-fittingcylindrical members therein unfavorably increases the manufacturingcycle time.

SUMMARY

Accordingly, articles for and methods of filling openings in objects,intended to address the above-identified concerns, would find utility.

One example of the present disclosure relates to an article for fillingan opening in an object. The article includes a plug having a body, afirst flange, and a second flange. The first flange is in contact withthe body and extends away from the body. The second flange is in contactwith the first flange and extends away from the first flange and thebody. The second flange is configured to deform toward the body uponinstallation of the plug into the opening. This deformation of thesecond flange rotationally and translationally secures the plug in theopening and consolidates the plug in the opening.

One example of the present disclosure relates to a method of frictionstir welding an object. The method includes performing a first frictionstir weld along a first weld path having an exit, with an opening formedin the object at the exit. The method also includes installing a pluginto the opening. The plug is consolidated in the opening and isrotationally and translationally secured in the opening uponinstallation. The method also includes performing a second friction stirweld along a second weld path traversing the opening that contains theplug installed therein. The plug is at least partially consumed in thesecond friction stir weld.

One example of the present disclosure relates to a method of installinga plug into an opening in an object. The method includes providing aplug having a body, a first flange, and a second flange. The firstflange is in contact with the body and extends away from the body. Thesecond flange is in contact with the first flange and extends away fromthe first flange and the body. The method also includes installing theplug into the opening to consolidate the plug in the opening and torotationally and translationally secure the plug in the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus described examples of the disclosure in general terms,reference will now be made to the accompanying drawings, which are notnecessarily drawn to scale, and wherein like reference charactersdesignate the same or similar parts throughout the several views, andwherein:

FIG. 1 is a block diagram of the article for filling an opening in anobject;

FIG. 2A is a side view of the article of FIG. 1;

FIGS. 2B and 2C are sectional views of a portion of the article of FIG.2A;

FIG. 3 is a process flow chart corresponding to a method of filling anopening in an object or of filling an opening in an object and frictionstir welding the object;

FIG. 4A is a schematic top view illustrating an opening formed in anobject by a first friction stir weld;

FIG. 4B is a schematic top view of the object shown in FIG. 4A, with theplug of FIG. 1 installed in the opening;

FIG. 4C is a schematic top view of the object shown in FIG. 4B afterperforming a second friction stir weld through the plug;

FIG. 5A is a sectional view of a portion of the article shown in FIG. 2Aprior to installing a plug thereof into an opening in an object;

FIG. 5B is a sectional view of the plug shown in FIG. 5A, superimposedover a virtual contour of the object;

FIG. 5C is a sectional view of the article of FIG. 1, with the pluginstalled in the opening of FIG. 5A and the second flange of the plugdeformed toward the body thereof;

FIG. 5D is a sectional view of the plug shown in FIG. 5C, installed inthe opening, with the shaft decoupled from the plug;

FIG. 5E is a sectional view of the plug shown in FIG. 5D, installed inthe opening, with the trailing end of the plug engaged by a frictionstir welding tool;

FIG. 5F is a sectional view of the object shown in FIG. 5E, with theplug consumed in the second friction stir weld;

FIG. 5G is a sectional perspective view of the plug shown in FIG. 2A,installed in an opening formed when two objects are friction-stir-weldedtogether;

FIG. 6 is a photograph of a section of an opening created by afriction-stir-welding tool;

FIG. 7A is a photograph of a top surface of an object having two sets ofintersecting friction-stir welds, wherein each intersection includes aconsumed plug;

FIGS. 7B and 7C are photographs of sections of the object of FIG. 7Aillustrating the consumed plugs;

FIG. 8 is a flow diagram of aircraft production and service methodology;

FIG. 9 is a block diagram of an aircraft.

In the block diagram(s) referred to above, solid lines connectingvarious elements and/or components may represent mechanical, electrical,fluid, optical, electromagnetic and other couplings and/or combinationsthereof. As used herein, “coupled” means associated directly as well asindirectly. For example, a member A may be directly associated with amember B, or may be indirectly associated therewith, e.g., via anothermember C. Couplings other than those depicted in the block diagram(s)may also exist. Dashed lines, if any, connecting the various elementsand/or components represent couplings similar in function and purpose tothose represented by solid lines; however, couplings represented by thedashed lines are either selectively provided or relate to alternative oroptional aspects of the disclosure. Likewise, any elements and/orcomponents, represented with dashed lines, indicate alternative oroptional aspects of the disclosure. Environmental elements, if any, arerepresented with dotted lines.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the presented concepts. Thepresented concepts may be practiced without some or all of thesespecific details. In other instances, well known process operations havenot been described in detail so as to not unnecessarily obscure thedescribed concepts. While some concepts will be described in conjunctionwith the specific examples, it will be understood that these examplesare not intended to be limiting.

Referring, e.g., to FIGS. 1, 2A, 2B, and 5A, one example of the presentdisclosure relates to an article 100 for filling an opening 404 (FIG.5A) in an object 400. The article 100 includes a plug 106 having a body112, a first flange 122, and a second flange 123. As shown, e.g., inFIG. 2B, the first flange 122 is in contact with the body 112 andextends away from the body 112. The second flange 123 is in contact withthe first flange 122 and extends away from the first flange 122 and thebody 112. The second flange 123 is configured to deform toward the body112 upon installation of the plug 106 into the opening 404. Thisdeformation of the second flange 123 rotationally and translationallysecures the plug 106 in the opening 404 and consolidates the plug 106 inthe opening 404. The deformation of the second flange 123 is discussedbelow, e.g., with reference to FIGS. 5A-5C. In some examples, the firstflange 122 may remain generally intact during deformation of the secondflange 123. The first flange 122 and the body 112 may delimit at least aportion of a gap 113 for receiving the second flange 123 during thedeformation thereof.

Referring, e.g., to FIG. 2A, in one aspect of the disclosure, which mayinclude at least a portion of the subject matter of any of the precedingand/or following examples and aspects, the article 100 also includes ashaft 102 frangibly coupled to the plug 106. The shaft 102 is decoupledfrom the plug 106 during installation of the plug 106 into the opening404, as further described below with reference to FIGS. 5C and 5D. Forexample, the shaft 102 may include a narrow neck 104 connecting theshaft 102 to the plug 106.

Referring to FIG. 2B, in one aspect of the present disclosure, which mayinclude at least a portion of the subject matter of any of the precedingand/or following examples and aspects, the plug 106 includes a trailingend 108. A portion of the trailing end 108 is configured to protrudeabove a surface 401 (FIG. 5D) of the object 400 when the plug 106 isinstalled into the opening 404 (FIG. 5A). Specifically, FIG. 5Dillustrates the plug 106 installed in the opening 404 with a portion ofthe trailing end 108 or, more specifically, a portion of the trailingsurface 110 extending above the surface 401 of the object 400.

Referring once again to FIG. 2B, in one aspect of the disclosure, whichmay include at least a portion of the subject matter of any of thepreceding and/or following examples and aspects, the article 100 mayalso include a third flange 124 and a fourth flange 125. The thirdflange 124 is in contact with the body 112 and extends away from thebody 112. The fourth flange 125 is in contact with the third flange 124and extends away from the third flange 124 and the body 112. The fourthflange 125 is configured to deform toward the body 112 and toward thefirst flange 122 upon installation of the plug 106 into the opening 404as, for example, shown in FIG. 5C. Similar to the deformation of thesecond flange 123, the deformation of the fourth flange 125 rotationallyand translationally secures the plug 106 in the opening 404 andconsolidates the plug 106 in the opening 404. The gap 113 between thefirst flange 122 and the third flange 124 may have the same size (e.g.,volume) as the size (e.g., volume) of the fourth flange 125 toaccommodate the deformation of the fourth flange 125 into the gap duringthe installation of the plug 106 into the opening 404. After theinstallation, the third flange 124 may remain generally intact, similarto the first flange 122.

The first flange 122 and the second flange 123 of the plug 106 form anarrangement of flanges. When additional arrangements of flanges arepresent, such as the third flange 124 and the fourth flange 125,described above, one flange in each of the arrangements may be receivedinto the corresponding gap 113 in a manner similar to the second flange123 and the fourth flange 125. The plug 106 may include, e.g., one, two,three, four, five arrangements of flanges, and so on. For example, FIG.2B illustrates the plug 106 having three such arrangements disposedalong the body 112. The first arrangement is formed by the first flange122 and the second flange 123, the second arrangement is formed by thethird flange 124 and the fourth flange 125, and the third arrangement isformed by the fifth flange 126 and the sixth flange 127. Adjacentflanges in contact with the body 112, e.g., the first flange 122 and thethird flange 124, may delimit at least a portion of the gap 113 forreceiving, e.g., the fourth flange 125 during the deformation thereofresulting from the installation of the plug 106 into the opening 404.Each additional arrangement of flanges further rotationally andtranslationally secures the plug 106 into the opening 404. Multiplearrangements of flanges may be distributed along the length of the plug106, providing frictional interference with the object 400 at differentlocations. Furthermore, for a given length of the plug 106 (generallycorresponding to the depth of the opening 404), increasing the number ofarrangements of flanges allows using smaller flanges that may be easierto deform.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the body 112 may have a frusto-conical shape. Furthermore, thecollective taper of the inner flanges, e.g., the first flange 122, thethird flange 124, and any other flange in contact with the body 112, maybe substantially the same as the taper of the opening. In one aspect ofthe disclosure, which may include at least a portion of the subjectmatter of any of the preceding and/or following examples and aspects,the fourth flange 125 has a smaller diameter than the second flange 123.It should be noted that the second flange 123 is disposed closer to thetrailing end 108 of the plug 106 than the fourth flange 125. This typeof the plug 106 may be used for tapered holes. Generally, a volume ofeach outer flange, e.g., the second flange 123, the fourth flange 125,and any other flange not directly in contact with the body 112, maycorrespond or, more specifically, may be substantially equal to thevolume of a corresponding gap 113 configured to receive such flange.This volume correspondence allows achieve full consolidation of the plug106 in the opening 404 once the plug is inserted into the opening.Furthermore, the difference between the outer and inner radii of eachouter flange, which may be referred to as a length of the flange, maynot exceed the height of the corresponding gap configured to receivesuch flange to ensure that the flange fits into the gap duringconsolidation of the plug 106 into the opening 404. For example, if thelength of the outer flange is greater than the height of the gap, theouter flange may bridge the gap rather than fit inside the gap.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the body 112, the first flange 122, and the second flange 123form a monolithic structure. For example, the body 112, the first flange122, and the second flange 123 may be machined from a single piece ofparent material.

In another aspect of the disclosure, which may include at least aportion of the subject matter of any of the preceding and/or followingexamples and aspects, the body 112, the first flange 122, and the secondflange 123 may be fabricated as separate components and then assembledtogether. For example, the first flange 122 may be removably attached tothe body 112, e.g., with a locational interference fit. The secondflange 123 may be removably attached to the first flange 122 in asimilar manner. In some aspects, the assembly of the plug 106 isperformed to accommodate the installation of the plug 106 into theopening 404 of a given size, and the flanges are selected based on thesize of the opening 404. In other words, the article 100 may be providedas a reconfigurable kit of multiple components. In one aspect, thearticle 100 may be supplied with multiple first flanges having differentsizes and/or multiple second flanges having different sizes toaccommodate openings of different size.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the body 112, the first flange 122, and the second flange 123are made of the same material. For example, the body 112, the firstflange 122, and the second flange 123 may be all made of aluminum,titanium, steel, bronze, copper, lead, plastic, or any other materialssuitable for friction stir welding. In some aspects, the material usedfor the body 112, the first flange 122, and the second flange 123 is thesame as the material of the object 400 containing the opening 404 forreceiving the plug 106.

Alternatively, in one aspect of the disclosure, which may include atleast a portion of the subject matter of any of the preceding and/orfollowing examples and aspects, the second flange 123 may be made of adifferent material than the first flange 122. For example, the secondflange 123 may be made from a material that is softer than the materialof the first flange 122, thereby allowing the second flange 123 todeform while maintaining the structure of the first flange 122substantially intact. Similarly, the body 112 may be made of a differentmaterial than the first flange 122 and/or the second flange 123.

Referring once again to FIG. 2B, in one aspect of the disclosure, whichmay include at least a portion of the subject matter of any of thepreceding and/or following examples and aspects, the second flange 123includes a slip feature 140 formed on a trailing outer corner 138 of thesecond flange 123. The slip feature promotes consolidation of the secondflange 123 into the gap 113 during installation of the plug 106 into theopening 404 by reducing friction between the trailing outer corner 138of second flange 123 and other surfaces, such as those of the plug 106.For example, during installation of the plug 106 into the opening 404,as illustrated in FIG. 5A, the trailing outer corner 138 may come incontact with a leading surface 139 of the trailing end 108 of the plug.In one aspect, the slip feature 140 may be implemented as a radius ofthe corner 138 and a chamfer on the corner 138.

In one aspect of the present disclosure, which may include at least aportion of the subject matter of any of the preceding and/or followingexamples and aspects, the second flange 123 includes an anchor feature136 formed on a leading outer corner 134 of the second flange 123. Theanchor feature 136 is configured to engage the surface of the insidewall of the opening 404 (FIG. 5A) during insertion of the plug 106therein. Once engaged with the surface of the opening 404, the anchorfeature 134 promotes deformation of the second flange 123 away from thedirection of insertion of the plug 106 into the opening 404 and towardthe body 112 of the plug into the gap 113. In one aspect, the anchorfeature may be an apical edge formed by two intersecting surfaces of thesecond flange 123.

As shown, e.g., in FIGS. 1 and 2C, the fourth flange 125 may include aslip feature 125 d formed on a trailing outer corner 125 c of the fourthflange 125. The fourth flange 125 may also include an anchor feature 125b formed on a leading outer corner 125 a of the fourth flange 125.Similarly, the sixth flange 127 may include a slip feature 127 d formedon a trailing outer corner 127 c of the sixth flange 127. The sixthflange 127 may also include an anchor feature 127 b formed on a leadingouter corner 127 a of the sixth flange 127. Likewise, any other outerflange, such as the second flange 123, may include a slip feature formedon its trailing outer corner and/or an anchor feature formed on itsleading outer corner.

In one aspect of the present disclosure, which may include at least aportion of the subject matter of any of the preceding and/or followingexamples and aspects flanges, such as the first flange 122 and thesecond flange 123, have an annular shape or a spiral shape. FIG. 2Billustrates the first flange 122 and the second flange 123 havingannular shapes. Specifically, the first flange 122 and the second flange123 are symmetric about a longitudinal axis of the opening 404 (FIG.5A). The plug 106 having annular flanges may be installed into theopening 404 by urging (linearly advancing and/or rotating) the plug 106into the opening 404 (FIG. 5A). The plug 106 having spiral flanges maybe installed into the opening 404 by linearly advancing the plug 106into the opening 404 and/or by rotating the plug 106 around thelongitudinal axis of the opening 404. For example, the plug 106 may havespiral flanges that correspond to a helical thread in the exit hole ofthe weld.

The disclosure and drawing figure(s) describing the operations of themethod(s) set forth herein should not be interpreted as necessarilydetermining a sequence in which the operations are to be performed.Rather, although one illustrative order is indicated, it is to beunderstood that the sequence of the operations may be modified whenappropriate. Additionally, in some aspects of the disclosure, not alloperations described herein need be performed.

As shown in FIG. 3, one example of the present disclosure relates to amethod of installing the plug 106 into the opening 404 in the object 400(FIG. 5A). The method of installing the plug 106 may be a part of themethod of friction stir welding the object 400 described below or may bea standalone method that does not include one or both friction stirwelding operations described below. The method of installing the plug106 may include providing the plug 106 having the body 112, the firstflange 122, and the second flange 123 (operation 304). As describedabove, the first flange 122 is in contact with the body 112 and extendsaway from the body 112. The second flange 123 is in contact with thefirst flange 122 and extends away from the first flange 122 and the body112. The method includes installing the plug 106 into the opening 404(operation 306) to consolidate the plug 106 in the opening 404 androtationally and translationally secure the plug 106 in the opening 404.Installing the plug 106 into the opening 404 may include urging the plug106 into the opening 404 thereby deforming the second flange 123 towardthe body 112 (operation 310).

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the second flange 123 includes the anchor feature 136 on theleading outer corner 134 of the second flange 123. As the plug 106 isurged into the opening 404, the anchor feature 136 grips a wall 405 ofthe opening 404, causing the second flange 123 to deform toward the body112. Various aspects of the anchor feature 136 are described above.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the second flange 123 includes a slip feature 140 on thetrailing outer corner 138 of the second flange 123. As the plug 106 isurged into the opening 404, the slip feature 140 allows the secondflange 123 to deform toward the body 112 by reducing friction betweenthe second flange 123 and other elements of the plug 106. Variousaspects of the slip feature 140 are described above.

As discussed above, the consolidation of the plug 106 in the opening 404may include deforming the second flange 123 toward the body 112. In someaspects, one or more additional outer flanges may be deformed during theoperation 306. The plug 106 may substantially completely fill theopening 404 and, preferably, leaves substantially no voids in theopening 404 after installation of the plug 106 therein. A sectional viewof the plug 106 installed into the opening 404 is shown in FIG. 5D. Theopening 404 may be created, for example, during a friction stir weldingoperation, as is further described below with reference to FIGS. 4A-4C.

FIG. 5A illustrates the plug 106 and the object 400 prior to installingthe plug 106 into the opening 404. Referring to FIG. 5B, it is apparentthat the radial dimensions of one or more outer flanges, such as thesecond flange 123, exceed those of the corresponding portion(s) of theopening 404. Those skilled in the art will appreciate that FIG. 5B is ahypothetical sectional view of an overlap between the outer flanges(e.g., the second flange 123) of the plug 106 and an imaginary objectprofile 510.

Accordingly, insertion of the plug 106 into the opening 404 duringoperation 310 causes one or more outer flanges, e.g., the second flange123, to deform, allowing the plug 106 to be fully inserted into theopening 404. As illustrated in FIG. 5C, the outer flange(s) are deformedinto the available gap(s). For example, the second flange 123 may beconsolidated into the gap between the first flange 122 and the trailingend 108. Similarly, the fourth flange 125 may be consolidated into thegap between the first flange 122 and the third flange 124. Additionalouter flanges may be deformed into gaps formed between correspondingadjacent inner flanges. Some deformation of the object 400, the innerflanges (e.g., flanges 122, 124, and 126) and the body 112 may alsooccur during installation of the plug 106 into the opening 404.

Referring generally to FIG. 3, one example of the present disclosurerelates to a method of friction stir welding the object 400 (FIG. 5E).The method includes performing a first friction stir weld 402 (FIG. 4A)along a first weld path having an exit 403 (operation 302). The firstfriction stir 402 weld causes the opening 404 to form in the object 400at the exit 403 of the weld path. The method also includes installingthe plug 106 (FIG. 4B) into the opening 404 (operation 306). The plug106 is consolidated in the opening 404 and is rotationally andtranslationally secured in the opening 404 upon installation. The methodalso includes performing a second friction stir weld 422 (FIG. 4C) alonga second weld path traversing the opening 404 that contains the plug 106installed therein (operation 316). The installed plug 106 is at leastpartially consumed in the second friction stir weld 422.

Each of these operations will now be described in more detail. FIG. 4Ais a top schematic view of the object 400 illustrating a first frictionstir weld 402 and the opening 404. The opening 404 is formed at theterminus of the first friction stir weld 402 as the welding tool exitsthe object 400. A sectional view of the opening 404 is provided in FIG.5A. In general, the opening 404 may vary in size and profile dependingon the design of the weld tool and on the thickness and type of theweld. For example, the weld tool may have tapered threads causingroughness on the side walls of the opening 404. However, not all weldtools have this feature.

FIG. 4B is a top schematic view of the object 400 illustrating the plug106 installed in the opening 404. A sectional view of the plug 106installed into the opening 404 is depicted in FIG. 5D. Another view ofthe plug 106 installed into the opening 404 is shown in FIG. 5G.Specifically, FIG. 5G is a sectional perspective view of two objects 520and 522, friction stir welded together and joined by a weld 524, withthe plug 106 installed into the opening 404 created by the weld 524. Theobjects 520 and 522 may be made from the same or different materials.The weld 524 is formed by combining (intermixing) plasticized materialfrom both objects 520 and 522.

FIG. 4C is a top schematic view of the object 400 showing anillustrative second friction stir weld 422, with the plug 106(represented as element 424) at least partially consumed therein. FIG.5F a sectional view of the friction stir weld 422 with the plug 106(represented as element 424) at least partially consumed therein.Preferably, the plug 106 is substantially completely integrated into theweld 424.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, installing the plug 106 into the opening 404 includes urgingthe plug 106 into the opening 404 during operation 310.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, urging the plug 106 into the opening 404 includes applying animpact to the plug 106 (block 312 in FIG. 3) and/or applying a torque tothe plug 106 (block 314 in FIG. 3). The impact may be applied to theshaft 102 frangibly coupled to the plug 106. This impact may decouplethe shaft 102 from the plug 106, as shown, e.g., in FIG. 5C. Likewise,the torque applied to the plug may decouple the shaft 102 from the plug106. FIG. 5D illustrates plug 106 without the shaft 102.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the plug 106 may be consolidated in the opening 404 bydeforming the flange 123 of the plug 106 toward the body 112 of the plug106. For example, the flange 123 may be deformed by urging the plug 106into the opening 404 (operation 310). As discussed above, the plug 106may include one or more outer flanges, such as the second flange 123.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the plug 106 is consolidated in the opening 404 substantiallywithout voids. Deformation of one or more outer flanges toward the bodyof the plug 106 fills the gaps 113 between the inner flanges (FIG. 2B).As such, once the plug 106 is installed into the opening 404 in theobject 400, there are substantially no voids between the plug 106 andthe object 400.

In one aspect of the disclosure, which may include at least a portion ofthe subject matter of any of the preceding and/or following examples andaspects, the plug 106 comprises the trailing end 108. At least a portionof the trailing end 108 protrudes from the opening 404 above the surface401 of the object 400 when the plug 106 is installed in the opening 404as, shown, for example, in FIGS. 5D and 5E. The trailing end 108 isurged into the opening 404 by a friction stir welding tool 512 duringthe second friction stir weld 422, as shown, for example, in FIG. 5E,which is a sectional view of the installed plug 106 illustrating thetrailing surface 110 of the trailing end 108 being engaged by thefriction stir welding tool 512. Through this engagement, the plug 106 isurged into the opening 404, thereby promoting plasticizing of the plugand intermixing it with the parent material of the object 400. Thetapered shape of the trailing surface 110 facilitates initial engagementof the trailing end 108 of the plug 106 by the friction stir weldingtool 512. In some aspects, to ensure smooth initial engagement of thetrailing end 108 of the plug by the friction stir welding tool, aportion of the trailing surface 110 may protrude below the surface 401of the object 400.

Experimental Results

FIG. 6 is a photograph of a section of an opening 606 within an object600 created by friction stir welding. For reference, the top surface ofthe object 600 is identified as an element 602, while the side wallsdefining the opening 606 are identified as an element 604. The opening606 is shown to have a taper. The opening 606 also has spirally orientedribs on the side walls 604, which may be created due to rotation of thewelding tool while it is removed from the object 600.

FIG. 7A is a photograph of a top surface of an object 700 having twosets 702 and 712 of overlapping welds, wherein each of overlaps 708 and718 includes a consumed plug. The overlap 708 was cross-sectioned in theY direction, and the result is presented in FIG. 7B. The overlap 718 wascross-sectioned in the X direction, and the result is presented in FIG.7C. FIGS. 7B and 7C illustrate complete filing of the overlaps 708 and718 and lack of voids in these areas.

Aircraft-Related Examples

An aircraft manufacturing and service method 800 shown in FIG. 8 and anaircraft 900 shown in FIG. 9 will now be described to better illustratevarious features of processes and systems presented herein. Duringpre-production, aircraft manufacturing and service method 800 mayinclude specification and design 802 of the aircraft and materialprocurement 804. The production phase includes component and subassemblymanufacturing 806 and system integration 808 of the aircraft.Thereafter, the aircraft may go through certification and delivery 810in order to be placed in service 812. While in service by a customer,the aircraft is scheduled for routine maintenance and service 814 (whichmay also include modification, reconfiguration, refurbishment, and soon). While the examples described herein relate generally to servicingof commercial aircraft, they may be practiced at other stages of theaircraft manufacturing and service method 800.

Each of the processes of aircraft manufacturing and service method 800may be performed or carried out by a system integrator, a third party,and/or an operator (e.g., a customer). For the purposes of thisdescription, a system integrator may include, without limitation, anynumber of aircraft manufacturers and major-system subcontractors; athird party may include, for example, without limitation, any number ofvendors, subcontractors, and suppliers; and an operator may be anairline, leasing company, military entity, service organization, and soon.

As shown in FIG. 9, aircraft 900 produced by aircraft manufacturing andservice method 800 may include airframe 902, interior 906, and multiplesystems 904 and interior 906. Examples of systems 904 include one ormore of propulsion system 908, electrical system 910, hydraulic system912, and environmental system 914. Any number of other systems may beincluded in this example. Although an aircraft example is shown, theprinciples of the disclosure may be applied to other industries, such asthe automotive industry.

Apparatus and methods embodied herein may be employed during any one ormore of the stages of aircraft manufacturing and service method 800. Forexample, without limitation, components or subassemblies correspondingto component and subassembly manufacturing 806 may be fabricated ormanufactured in a manner similar to components or subassemblies producedwhile the aircraft is in service.

Also, various features described herein may be utilized during aircraftcomponent and subassembly manufacturing 806 and/or during systemintegration 808, which may expedite assembly of or reducing the cost ofthe aircraft. In some examples, these features may be utilized while theaircraft is in service, for example, during maintenance and service 814of the aircraft.

Different examples and aspects of the apparatus and methods aredisclosed herein that include a variety of components, features, andfunctionality. It should be understood that the various examples andaspects of the apparatus and methods disclosed herein may include any ofthe components, features, and functionality of any of the other examplesand aspects of the apparatus and methods disclosed herein in anycombination, and all of such possibilities are intended to be within thespirit and scope of the present disclosure.

Having the benefit of the teachings presented in the foregoingdescription and the associated drawings, many modifications of thedisclosed subject matter will become apparent to one skilled in the artto which this disclosure pertains. Therefore, it is to be understoodthat the disclosure is not to be limited to the specific examples andaspects provided and that modifications thereof are intended to bewithin the scope of the appended claims. Moreover, although theforegoing disclosure and the associated drawings describe certainillustrative combinations of elements and/or functions, it should beappreciated that different combinations of elements and/or functions maybe realized without departing from the scope of the appended claims.

What is claimed is:
 1. A method of friction stir welding an object, themethod comprising: performing a first friction stir weld along a firstweld path having an exit, wherein an opening is formed in the object atthe exit; installing a plug into the opening, wherein the plug isconsolidated in the opening and is rotationally and translationallysecured in the opening upon installation; and performing a secondfriction stir weld along a second weld path traversing the opening thatcontains the plug installed therein, wherein the plug is at leastpartially consumed in the second friction stir weld.
 2. The method ofclaim 1, wherein installing the plug into the opening comprises urgingthe plug into the opening.
 3. The method of claim 2, wherein urging theplug into the opening comprises applying an impact to the plug.
 4. Themethod of claim 3, wherein the impact is applied to a shaft frangiblycoupled to the plug, and wherein the impact decouples the shaft from theplug.
 5. The method of claim 2, wherein urging the plug into the openingcomprises applying a torque to the plug.
 6. The method of claim 1,wherein the plug is consolidated in the opening by deforming a flange ofthe plug toward a body of the plug.
 7. The method of claim 6, whereinthe flange is deformed by urging the plug into the opening.
 8. Themethod of claim 6, wherein the body has a frusto-conical shape.
 9. Themethod of claim 6, wherein the plug contacts the body afterinstallation.
 10. The method of claim 9, wherein: the flange is a secondflange, a first flange of the plug is in contact with the body andextends away from the body; and the second flange shears from the firstflange and consolidates into a gap toward the body upon installation.11. The method of claim 10, wherein, prior to installation: the secondflange is in contact with the first flange and extends away from thefirst flange and the body; and the first flange and the body delimit atleast a portion of the gap.
 12. The method of claim 10, wherein a volumeof the gap is substantially equal to a volume of the second flange. 13.The method of claim 1, wherein the plug is consolidated in the openingsubstantially without voids.
 14. The method of claim 1, wherein: theplug comprises a trailing end, at least a portion of the trailing endprotruding from the opening above a surface of the object when the plugis installed in the opening, and the trailing end is urged into theopening by a friction stir welding tool during the second friction stirweld.
 15. A method of installing a plug into an opening in an object,the method comprising: providing a plug comprising a body, a firstflange, a second flange, and a gap, wherein: the first flange is incontact with the body and extends away from the body, the second flangeis in contact with the first flange and extends away from the firstflange and the body, the first flange is disposed between the secondflange and the body and separates the second flange and the body, andthe first flange and the body delimit at least a portion of the gap; andinstalling the plug into the opening to consolidate the plug in theopening and to rotationally and translationally secure the plug in theopening, wherein the second flange shears from the first flange andconsolidates into the gap toward the body and contacts the body uponinstallation.
 16. The method of claim 15, wherein, upon installation,the second flange fills the gap substantially without voids.
 17. Themethod of claim 15, wherein a volume of the gap is substantially equalto a volume of the second flange.
 18. The method of claim 15, whereininstalling the plug into the opening comprises urging the plug into theopening thereby deforming the second flange toward the body.
 19. Themethod of claim 18, wherein: the second flange comprises an anchorfeature on a leading outer corner of the second flange, and as the plugis urged into the opening, the anchor feature grips a wall of theopening, causing the second flange to deform toward the body.
 20. Themethod of claim 18, wherein: the second flange comprises a slip featureon a trailing outer corner of the second flange, and as the plug isurged into the opening, the slip feature allows the second flange todeform toward the body by reducing friction between the second flangeand other elements of the plug.